Objective: To evaluate the efficiency of enhanced depth imaging optical coherence tomography (EDI-OCT) on quantifying choroidal thickness (CT) in normal subjects.
Methods: This was a cross-sectional study. From June to November 2011, 129 eyes of 129 normal subjects were enrolled in this study and divided into three groups by age distribution. Group A, 43 eyes, 22 to 40 years old; group B, 42 eyes, 41 to 60 years old and group C, 44 eyes, 61 to 79 years old. They were examined with EDI-OCT for CT. The choroid was measured from the posterior edge of the retinal pigment epithelium to the choroid-scleral junction at 500 µm intervals of a horizontal section from 3 mm temporal to the fovea to 3 mm nasal to the fovea. The paired t test was used to analyze differences in CT by location in the macula. One-way analysis of variance (ANOVA) was conducted to compare mean CT in different groups. Subsequently the data between two groups were analyzed by least significant difference (LSD-t). The reliability was evaluated by intraclass correlation coefficient (ICC).
Results: The choroid was thickest beneath the fovea (305.9 ± 78.2) µm. The mean CT decreased rapidly in the nasal direction and gradually in the temporal direction, reaching (159.0 ± 67.3) µm at 3 mm nasal to the fovea and (256.8 ± 73.6) µm at 3 mm temporal to the fovea. There was a significant difference between subfoveal CT and CT at all extrafoveal locations (t = 4.021 to 34.544, P < 0.05). There was also a significant difference of CT at all locations among three age groups (F = 34.122 to 72.239, P < 0.05). CT was significantly greater in group A than group B and C at all locations (P = 0.000, 0.000). It was also significantly greater in group B than group C (P = 0.000). The inter-examination ICC values ranged from 0.979 to 0.996. The intraobserver ICC values ranged from 0.981 to 0.997. The interobserver ICC values ranged from 0.971 to 0.995.
Conclusions: Normal CT can be measured accurately by EDI-OCT. There are significant differences of CT between different age groups in normal subjects.